The Lunar Electromagnetic Monitor in X-rays (LEM-X) is an imager for X-ray Astronomy to be installed on the surface of the Moon, is funded by the Italian Ministero dell’Università e della Ricerca Scientifica and lead by the Istituto Nazionale di Astrofisica in the framework of the Italian “Piano Nazionale di Ripresa e Resilienza”. The building block of LEM-X is represented by a pair of coded aperture cameras, each one built around four large-area linear Silicon Drift Detectors and able to image the sky within a field of view of ~1 sr with a source location accuracy of ~1 arcmin, while at the same time reaching a spectral resolution better than 350 eV FWHM at 6 keV. The LEM-X instrument preliminarily envisages about seven such camera pairs, arranged on a dome-like structure on the surface of the Moon, to reach a sensitivity better than 5 mCrab in 50 ks and 1 Crab in 1 s in the 2 – 50 keV energy band. In this contribution we describe the design of LEM-X, we discuss the scientific performance and we report the status of the instrument development.
The Lunar Electromagnetic Monitor in X-rays (LEM-X) is a proposed lunar observatory for the study of high-energy transients. The fundamental components of the LEM-X instrument are pairs of coded aperture cameras, each sensitive in the 2−50 keV range and with a 2 sr field of view. In this paper, we present a trade-off analysis of the instrument layout, identify the optimal design, and characterize its performance in terms of sky exposure for multiple candidate landing sites. We first optimized the number and configuration of cameras and designed a concept of their support structure, to ensure complete and uniform sky coverage while minimizing complexity and volume. Then, by using NASA’s SPICE toolkit, simulations were carried out to assess the effective sky coverage of the proposed instrument configuration. We provide results for three landing site candidates on the Moon’s prime meridian, with latitudes 0°, −70° and −90°, laying the groundwork for future mission implementation studies.
The Solar X-Rays MOONitor is a project aimed at demonstrating the feasibility and the technological maturity of a lunar-based space weather monitor relying on a commercially available sensor. The results of a test campaign performed in favor of an analogous instrument (SolarX) demonstrated an energy resolution suitable to assess the solar corona plasma temperatures and energies.
Next activities are oriented to realize a Digital Pulse Processor readout electronics implemented in such a way that, in the future, it can be built with space-qualified components. The system shall be able to manage flux variations of several orders of magnitude to deal with the extreme Sun conditions: from quiet to the most energetic class-X flares. Beside this, an activity to identify which are the possible signatures of solar events is on-going.
This paper reports the current and the planned activities to implement the sensor’s readout functions in an FPGA-based space-ready electronics.
The Lunar Electromagnetic Monitor in X-rays (LEM-X) is a proposed observatory on the Moon surface for the detection of transients and the long-term monitoring of astrophysical sources across the whole observable sky in the 2 − 50 keV band. LEM-X is based on a compact and lightweight coded-aperture camera with a 2 sr field of view. The detector plane is composed of four individual alumina-based Detector Assemblies (DA), each one hosting a single large-area (∼ 7 × 7 cm2) linear Silicon Drift Detector (SDD), as well as 24 analog Application Specific Integrated Circuits (AFE ASICs), specifically developed for this project. High-voltage cables and a rigid-flex printed circuit board connect the DA to the back-end electronics and power supply. A breadboard featuring a 64-channel SDD and two AFE ASICs has been manufactured and is currently under test. The LEMX DA is being developed within the Earth-Moon-Mars project of the Italian National Recovery and Resilience Plan.
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